Eco-cement, the cheapest carbon sequestration on the planet

By Prof. John Mathews, Macquarie Graduate School of Management, Australia Cement production is one of the dirtiest industrial processes on the planet. It produces nearly 9% of global carbon emissions. This increases every year with the extraordinary demands for building materials in China and India. But it is set to become much greener: cements and concretes of the future will sequester vast amounts of carbon dioxide (CO2) and utilise huge volumes of industrial wastes in the form of additives. Cement (and the concretes made with it) are about to become carbon negative – absorbing more carbon that they produce. It will happen by mimicking nature – in this case, the process through which marine organisms build shells. It is not widely appreciated that the most substantial process of carbon sequestration on the planet is accomplished by myriad marine organisms making their exoskeletons, or shells. Shells are produced biologically from calcium and magnesium ions in sea water and carbon dioxide from the air, as it is absorbed by sea water. When the organisms die, their shells disintegrate and form carbonate sediments, such as limestone, which are permanent, safe carbon sinks. We can emulate this natural process by producing cement, concrete and other composite construction materials that are “shell-like”. They contain synthetic calcium and magnesium carbonate, and are produced at temperatures far below those employed in conventional kilns. The calcium and magnesium have to be sourced industrially (and there are various promising routes, quite apart from mining the stuff). The carbon comes from the air – from our releases via combustion of fossil fuels and ordinary cement production. This is biomimicry in action – or what the Australian geoscientist John Harrison calls geomimicry – emulating geological processes such as weathering ...Zum vollständigen Artikel